System and method for biomass combustion

Abstract

Disclosed is a system and method for the combustion of biomass material employing a swirling fluidized bed combustion (SFBC) chamber, and preferably a second stage combustion carried out in a cyclone separator. In the combustion chamber, primary air is introduced from a bottom air box that fluidizes the bed material and fuel, and staged secondary air is introduced in the tangential direction and at varied vertical positions in the combustion chamber so as to cause the materials in the combustion chamber (i.e., the mixture of air and particles) to swirl. The secondary air injection can have a significant effect on the air-fuel particle flow in the combustion chamber, and more particularly strengthens the swirling flow, promotes axial recirculation, increases particle mass fluxes in the combustion chamber, and retains more fuel particles in the combustion chamber. This process increases the residence time of the particle flow. The turbulent flow of the fuel particles and air is well mixed and mostly burned in the combustion chamber, with any unburned waste and particles being directed to the cyclone separator, where such unburned waste and particles are burned completely, and flying ash is divided and collected in a container connected to the cyclone separator, while dioxin production is significantly minimized if not altogether eliminated. A Stirling engine along with cooling system and engine control box is integrated with the SFBC chamber to produce electricity from the waste combustion process. Residual heat in the flue gas may be captured after the combustion chamber and directed to a fuel feeder to first dry the biomass. System exhaust is directed to a twisted tube-based shell and tube heat exchanger (STHE) and may produce hot water for space heating.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application is a continuation-in-part of copending U.S. patent application Ser. No. 16 / 378,986 entitled “SYSTEM AND METHOD FOR BIOMASS COMBUSTION” filed with the U.S. Patent and Trademark Office on Apr. 9, 2019, which application is a continuation of U.S. patent application Ser. No. 15 / 056,179 entitled “SYSTEM AND METHOD FOR BIOMASS COMBUSTION” filed with the U.S. Patent and Trademark Office on Feb. 29, 2016, now U.S. Pat. No. 10,253,974 issued on Apr. 9, 2019, which is based upon and claims benefit of copending U.S. Provisional Patent Application Ser. No. 62 / 121,843 entitled “Method and Design of the Ultra-Clean Mobile Combustor for Waste Biomass and Poultry Litter Disposal,” filed with the U.S. Patent and Trademark Office on Feb. 27, 2015 by the inventor herein. This application is also based upon and claims benefit of copending U.S. Provisional Patent Application Ser. No. 63 / 089,760 entitled “Efficient and Innovative Drying Process...

AI Technical Summary

Benefits of technology

The patent is about a system and method for ultra-clean and efficient combustion of biomass and poultry litter. The system is compact and easy to operate, and can burn waste with high efficiency while reducing emissions of pollutants. The single chamber design reduces capital costs compared to multiple chamber systems. The system produces more electricity, has lower maintenance costs, and is more flexible regarding fuel sources and conditions. Overall, this system provides a affordable and environmentally friendly solution for disposing of biomass and poultry litter while generating energy.

Problems solved by technology

However, as the industry consolidated, operations became highly regionally concentrated, and cropland diminished, this waste disposal method became less viable.

In fact, agriculture has been identified as the single largest source of pollutants for rivers, lakes, and estuaries in the U.S. The industrialization of agriculture has resulted in such high concentrations of animal waste such that conventional disposal methods are no longer adequate or viable (i.e., spreading on fields).

However, due to the relatively low energy density of biomass, the economics of biomass-to-energy conversion technologies have been challenging (e.g., fuel collection and transportation costs can be high relative to energy density; high moisture content adds to transportation costs and reduces burn efficiencies).

However, widespread commercial acceptance of such prior systems has been lacking, due to an inability to reach sufficiently high combustion efficiencies and minimization of noxious emissions.

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